Bacteriophage: A Useful Tool for Studying Gut Bacteria Function of Housefly Larvae, Musca domestica.

Beneficial symbiotic bacteria have positive effects on some insects' (such as mosquitoes, cockroaches, and flies) biological activities. However, the effects of a lack of one specific symbiotic bacterium on the life activities of some insects and their natural gut microbiota composition remain unclear. Bacteriophages are viruses that specifically target and kill bacteria and have the potential to shape gut bacterial communities. In previous work, Pseudomonas aeruginosa that naturally colonized the intestines of housefly larvae was shown to be essential to protect housefly larvae from entomopathogenic fungal infections, leading us to test whether a deficiency in Pseudomonas aeruginosa strains in housefly larvae that was specifically caused using bacteriophages could remold the composition of the intestinal bacteria and affect the development of housefly larvae. Our research revealed that the phage, with a titer of 10 PFU/ml, can remove 90% of Pseudomonas aeruginosa in the gut. A single feeding of low-dose phage had no effect on the health of housefly larvae. However, the health of housefly larvae was affected by treatment with phage every 24 h. Additionally, treating housefly larvae with bacteriophages every 24 h led to bacterial composition changes in the gut. Collectively, the results revealed that deficiency in one symbiotic gut bacteria mediated by precise targeting using bacteriophages indirectly influences the intestinal microbial composition of housefly larvae and has negative effects on the development of the host insect. Our results indicated the important role of symbiotic gut bacteria in shaping the normal gut microbiota composition in insects. The well-balanced gut microbiota ensures appropriate development of the host insect, such as mosquitoes, cockroaches, and flies. Various intestinal symbiotic bacteria have different influences on the host gut community structure and thus exert different effects on host health. Therefore, it is of great importance to understand the contributions of one specific bacterial symbiont to the gut microbiota community structure and insect health. Bacteriophages that target certain bacteria are effective tools that can be used to analyze gut bacterial symbionts. However, experimental evidence for phage efficacy in regulating insect intestinal bacteria has been little reported. In this study, we used phages as precision tools to regulate a bacterial community and analyzed the influence on host health after certain bacteria were inhibited by bacteriophage. The ability of phages to target intestinal-specific bacteria in housefly larvae and reduce the levels of target bacteria makes them an effective tool for studying the function of gut bacteria.